Data processing systems include memory devices for storing, processing, and moving data. A memory device, or memory, is generally a physical component of a data processing system configured to store data. A memory may also include logical or virtual components, such as a space on a hard disk designated to be used as a part of the memory.
Real memory is the amount of memory available on a physical memory device, excluding any logical or virtual memory structures. A data processing system needs memory to perform an operation, including starting from a power-off mode or shutdown status. A boot process, or booting up, is the process of bringing a data processing system from a power-off mode or a shutdown status to a point where the operating system is successfully loaded and the data processing system is operational for performing additional tasks. In some cases, the successful loading of the operating system presents a command prompt to a user, and in other cases, the boot process may couple with other processes, such as to present a graphical user interface to a user, launch certain applications, or establish communications with certain entities over a data network.
Memory is an essential part of the boot process. Particularly, some amount of real memory is required for loading certain components of an operating system so that the boot process may complete and the data processing system may become operational for the desired purpose.
Data processing systems can be configured in a variety of ways. For example, the components in a data processing system may be configured to operate in a manner such that parts of the data processing system behave as separate data processing units. The memory in such a configuration can be associated with a single data processing unit and can be used for the boot process, such as to load components of the data processing unit's operating system.
As another example, data processing systems can be divided into logical partitions (LPARs). Such data processing systems are also known as logically partitioned data processing systems. A logical partition is also known simply as a “partition.” Each partition operates as a separate data processing system independent of the other partitions. Generally, a partition management firmware component manages the various partitions and provides the network connectivity among them. A Hypervisor is an example of such a partition management firmware. Memory in such configurations is divided and allocated to the various partitions. A partition's boot process uses the memory allocated to that partition to load the operating system image for that partition.